The primary goal is to investigate the functional organization of motion computations in visual cortex. Primate area MT is intimately linked to the perception of motion and the generation of eye movements, yet little is known regarding the functional role of each of its multiple sources of convergent input. This information is critical to our understanding of how neural circuits underlie perception and behavior, and may have important implications for disorders of the visual system. The proposed studies will focus on primate area MT and will assess the specific contributions of inputs from V2 using reversible inactivation and two photon microscopy. We will first retrogradely label cells that project from V2 to MT and image their activity using two-photon microscopy. The visual response properties of MT-projecting cells will be characterized and compared to other cells nearby and across functional compartments within V2. Of particular interest will be response properties thought to be computed first within MT as well as those thought to be relayed to MT through V2 rather than other known input pathways. Next, we will reversibly inactivate V2 with chilled methanol perfused through coils implanted into the lunate sulcus. MT response properties and behavioral performance can then be measured in the awake, behaving macaque monkey with and without an active V2. Special emphasis will be given to investigating the role of V2 in providing MT with direction of motion and binocular disparity information. This research will lead to a better understanding of how our brain processes a visual scene and mediates our ability to perceive moving objects. Not only will this information elucidate the complex processes of the healthy brain, but it will also give us important insight into the brain regions affected by aging and mental disease. In particular, several mental disorders such as schizophrenia and Parkinson's disease have selective deficits in visual motion perception, and a better understanding of the neural mechanisms involved in these conditions may inform efforts to alleviate these symptoms